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Mucolytic agents and otitis media with effusion
J E Fitzgerald1, G G Green, J P Birchall
1Department of Physiological Sciences, University of Newcastle upon Tyne; UK.
Abstract:
Middle ear effusion was obtained from children with otitis media with effusion and separated into thick (mucoid) and thin (serous) pools. Both effusion types contained similar amounts of non-dialysable solids. However, the thick effusions contained more mucus glycoprotein than the thin effusions, 25% and 8.2% respectively. Amino acid and carbohydrate analysis of the CsCl purified mucus glycoproteins demonstrated that the glycoprotein from the thick and thin effusions differed in their protein core, those from the thick effusions possessing a higher percentage of serine and threonine, the amino acids to which the sugar side-chains attach. They are also more glycosylated. N-acetyl cysteine and mercaptoethanol caused a fall in the viscosity of solutions of purified middle ear glycoprotein and effusion homogenate. However, longer term incubation caused a rise above the starting viscosity. This effect was concentration-dependent, and was mediated by low molecular weight components in the effusion and not the mucus glycoprotein. S-carboxymethyl cysteine had no effect on the viscosity of either the purified mucus glycoprotein or the effusion homogenate. Therefore, to produce a decrease in effusion viscosity in vivo, the concentration of mucolytic reaching the middle ear and the time it remains there are critical factors.
Insights
Thick middle ear effusions contain more mucus glycoproteins than thin ones, differing in protein structure. Mucolytic agents can reduce effusion viscosity, but concentration and contact time are critical for effectiveness.
Area of Science:
- Biochemistry
- Otolaryngology
Background:
- Otitis media with effusion (OME) is common in children.
- Middle ear effusions (MEE) can be categorized as mucoid (thick) or serous (thin).
Purpose of the Study:
- To analyze the composition and properties of MEE.
- To investigate the viscosity-modifying effects of mucolytic agents on MEE.
Main Methods:
- Separation of MEE into thick and thin pools.
- Biochemical analysis of mucus glycoproteins (amino acid, carbohydrate composition).
- Viscosity measurements of MEE and purified glycoproteins with mucolytic agents.
Main Results:
- Thick MEE had significantly higher mucus glycoprotein content (25%) than thin MEE (8.2%).
- Mucus glycoproteins from thick MEE had different protein cores with higher serine and threonine content and increased glycosylation.
- N-acetyl cysteine and mercaptoethanol reduced MEE viscosity, but viscosity increased upon longer incubation, mediated by low molecular weight components.
Conclusions:
- Middle ear effusion viscosity is influenced by mucus glycoprotein composition and low molecular weight components.
- Effective reduction of MEE viscosity in vivo requires optimizing mucolytic concentration and contact time.